Brake release



INVENTOR :Ku/M

- @MMZ AT TOR N EY `July 23, 1957 K. SCHNEIDER 2,800,205

BRAKE RELEASE Filed June l, 1954 3 SheeLs--Sheel 2 v c 55 5 7 ,/y. 3. 5? 5 70 l 53 7/ X 57 Q2 65 55 /f sa l! f /72 0 7/ o o `o 7/ it "70 ,f aa 7411 75- O o o 75 O a@ 37 77 OPO g?. 82 n 7/ 7/ 5/ 4 v 772 :NVENTOR 3' BY f7 @MMM LM ATTORNEY `Iuly 23, 1957 K. SCHNEIDER 2,800,205

BRAKE RELEASE Filed June l, 1954 3 Sheets-Sheet 3 /g- J l INVENTOR ATTORNEY nite j songes Patented July 23, 1957 Y 2,830,205'I BRAKE RELEASE r 4 Karl Schneider, Greenfield, Wis., assignor to Hamisch- States Patent 955C@A v is necessary without impairment of the rapidity of feger Corporation, Milwaukee, Wis.,r a corporation of r Wisconsin Y Application June 1, 19754, Serial No.` 433,666 j ,y

` 11 ClmS. (Cl. 18S-216) This invention relates to friction brakes as may `be employed in conjunction with the hoist and dragline cable.

spools of a dragline excavator, and it more Specifically resides in a brake having a brake drum with a brake band` i in facing relation 'to the drum that is adapted to bewrapped tightly about the drum in a brake set position-i and to be radially shifted away from `the drum intova brake released position, there being provided brake` re-j'` leasing means attached to the band for drawingthe band from the drum and supporting the same in a position free of contact with the drum, which releasing means exerts af;

force upon the band to urge it away from the drum only upon placing the brake in released position.

To actuate a brake band disposed about a circumfer-j' ential portion of a brake drum it is usual to cause a circumferential shift of one end ofthe band relative-to the opposite end. By relatively drawing the ends towardone another the band diameter is reduced, with a wrapping of v the band tightly against the drum being -accomplishedito i effect braking action. A relativeshift of theends `from one another increases band diameter and releases theV band from engagement with the drum. This movement permits radial spacing of theband fromthe drum, Tand 'for i, a satisfactory brake release the band should standback from the 'drum along its entire circumference. For lightweight bands of thin cross section a resilient material may be'ernployed that tends to spring radially outwardly with,`

sutlicient force to sustain its own weight.' For brake released position such a band will stand clear of frictionalj In the adaptation of the i band type brake tolarger brake sizes the shear weight of engagement with the drum.

brake responsa port l of .,a br`ake b and in` spacedzrelation to a brake .drum uponfdisposingthe brake-inreleased position to prohibit frictional drag of the bandagainst'the drum.' i

It` is another object'ofithis invitation to provide brake releasing actuators in a brake for applying a force to the brake band that is present only during periods of brake 1 l0 release@y v It is another object of this invention to .provide a brake employing a brake band in conjunction with a brake drum in which the size of `the band members may be increased, tol handle increased loads, without` an accompanying collapse of such a band of greater weight against the drum Y ,l when `the brake is placed in released position.

It is another object of this invention to provide a brake having a drum and encircling band in which releasing actuatorsffor the band are employed to present a positive quick brake-release with a rapid response to the actuation thereof.

the band may, however, cause it to sag and brushagainst i the drum-when in brake released position.r

For the larger brake sizes resort may be made tothe use of a brake shoe arrangement, thus eliminating a band that would, by reason of its own weight, collapse against the drum when moved to released positiom Such resort, however, introduces problems unique tothe brake shoe construction, such as diiiiculty in attaining uniform gn'pping and diicultyin timing the braking and releasingy motion of the individual shoes for attaining simultaneous action. Special constructions have been employed to support brake bands in spaced relation to the drum when released. f Bias springs acting to draw the band radially It is another object of this invention to provide in a brake having a drum and bandin facing relation to the drum, for uniform spacing `between the band and drum along the length of the band, upon placing the brake in released position. v

These and otherobjects and advantages of this inven-` tion will appear inthe'description to follow. In the description referenceis made to the` accompanying drawings, in which there .is shown by way of illustration and not of limitation, specic forms in which this invention maybe embodied.

In the drawings:

Fig, 1 is a right hand side view in elevation of a dragline excavator in ,which this invention is embodied,

Fig. 2 is a left hand side view in relevation of the dragline cable spoolof the dragline excavator in Fig. l'show-y ing the holding brake employed in connection with such spool, i

Fig. 3 is a right hand side View in elevation of the hoist cable spool of the dragline 'excavator in. Fig. l showing thetholding brake `employed vin connection with such l upon a crawler frame 3. A tiltable boom 4 'extends' forfrom the drum, thus compensating for band weight,`are

one form of such construction. In this construction, however, a positive bias force is appliedV to the band at all times which is in opposition to a movement of the band into the braking position. `An oversize actuator for shifting the band to braking position is now required and inertia factors are introduced that may cause brake action to become unduly sluggish.

The present invention provides a support for the band that applies a forcefor drawing the band from the drum only when the brake is released. The supporting force is not present during application of braking action, but instead is applied only when required. This permits the use of the brake band construction where larger braking Cawardly at an incline from the front of the cab 2, and also extending from the front of the cab 2 is a tiltable mast 5 that extends above the lower end portion ofthe boom 4.

Secured `to the base of the cab 2 and rising upwardly above the roof of the cab 2 is a gantry 6. The gantry 6 has a right side tension member 7 and a right side compression member 8 that are joined at their upperl ends by a gusset plate 9. The gantry 6 also comprisesleft side i tension and compression members similar to the members Y 7 and 8, which arenot shown.l

Extending between the top of the gantry 6 and the upper extremity of the mast 5 is a boom hoist line`10.` The line 10 comprises several runs between the gantry 6 and mast 5 and one end passes` downwardly to a boomdioist drum 'within the cab 2, that is not shown. By drawing in or paying out theline 10 the boom 4 may be raised or lowered. A stay line 11' ofrixed length runs from the upper extremity of the mast 5 to the upper end of the boom- 4. Additional stay lines 12 and 413 are strung betweenthe upper end of the mast 5 and points along the boom 4,"as shown, to provide necessary support for Itis-an object ofthisinvention to provideffor the'sup-A upper end. of. the mast and a similar' hoist cable sheave.

is rotatably mounted at Ythe upper end of'theaboom 4. Mounted withinrthe cab 2'is a hoist` cablerspoolassembly 16 .and running upwardly froml the assembly 16-is a hoist.

cable 17j that passes about the sheave 14 and continuesV upwardly and forwardlyto the sheave 15;, TheL hoist cable 17 then passes aboutthe'sheave lfanddrops downwardly. therefrom for, attachment at its free end 18=with azbailchain. 19 of a dragline bucket 20.

A twin sheave fairlead 21 is mounted at the fronti` ofvv thecab.2.tl1`rough which is'led: a dragline cabl'e22 "Ehe cable.22*is deadended upon. a dragline cable spool? assern blyy 23Lmounted within the cab 2 tothe front of thezhoist cabletspool assembly 16Y and runs outwardly from the twin sheave fairlead 21 to a connection with a dra'gline4 chain 24. Thecable 22` is also connectedi with the bail chain 19 andan integralL bail'25? at2 the: openlend'wofl the draglinez bucket 20.

The spool assemblies 23. and 1'6'- are viewed'in Figs, 2

and .3, respectively, from'v the tends at which-holding-brakes',v to be described and forming a part thereof, are located. Referring'rst to Fig` 2, .there:i's1 shown a: left: side end view of the dragline cable. spool assembly 23:I taken on a.

section througha rotatable drive'. shaft 26. Driving means: for theishaft 26 is not' shown, and may be ofiknowniorm.

The shaft 26 mounts a cable spool 27 upon whichr is wound' the dragline cable' 22. The spool 27 may-.be caused to rotatef in either direction by control means, also notv shown, and secured to the cable spool 27' isan axially extending brake drumz 28 of a brake generally designatedbythenumeral 110. A.shroud plate-29 bolted tol a hub1 30 on the shaft 26 encloses the interior offthe drum 28;

Surrounding the brake drum 28 isi ay flexible brake bandi 311 formed in. two sections. joinedV together as `shown at 33. A plurality lofzbrake lining segments 32" are secured=V to the: band 31 infacing relation to' the drum 28. As

shownzin Fig. 2, the brake lining segments 32 may be brought up tightly. against the outer circumferential face of the drum 28 to eect a braking action to restrainvro tation of the-spool 27. t

Onel end. of. ther flexible brake band 3'1 is v secured- =to a link 34 thatl is attached through a pivotal connection witha supporting frame 35 rising from a deck plate 112 oftheA cab 2. The link 34-restrains the associated eind of.' the brake band 31, fromy moving. circumferentially, but through its pivoted connection with` the frame 35 permitsandthe right hand end of the channel member 49 is secured to avertical member- 51` that inturn issupported upon a main frame member 52, a portion only of which is shown. Disposed on the radially inner face of the curved channel member 49 is a group of three brake band release support assemblies 53, one of which is clearly shown in Fig. 4.

the end ofthe band 31 to-be moved radially inwardly Y against the brake drumv 28 andradially' outwardly tovbe` cylinder- 41 is provided with a iiexible-air inlet hose 42 Y andis'mounted upon a plate 43attached to and forming a part ofa bracket 44' that may be swung about' a pivotal connection withtheear 38.` A small'ear 45 on'the underside of the plate 43 connects with*l a bolt' 46that passes through a plate 47 extending-from the supporting frame 35. The bolt 46 is fixed in` relationto the plate' 47 by'a i setof'lock nutsV 48,'- and-thus through adjustment of`r the` bolt 46 the'brake settingiand releasing-cylinder 41 may be= disposed in a particular'position desired.

'A curved channel memberr49 is uniformly' spacedl radially outwardly'from thatlportion of'the brake band 311' above the brake drum 28. V,Theleft hand4 end' of the channel member 49; as viewed in Fig; 2; isbolted toV aU bracket 50 rising upwardly from tlie'supporting-frame35',

An assembly 53 comprises a mounting bracket 54 welded to the channel member-49, to which are secured a pneumatic release support cylinder 55. and an adjustable pivot support bolt 56. Thebolt 5.6 isbifurcated.' at. one end that mounts a pivot pin 57, upon which is borne aA link 58 that rides between the bifurcations of the bolt 56. The penumatic release support` cylinder 55-has= :air air inlet hose 59 and extending from-the'underside of the cylinder 55 is a piston stem 60 disposed in a position to bear l against one end of the link 58. The opposite end of the link 58 is pivotally joined to a connecting link 61 which infturn is-.pinned to an earI 62rv attached to-the'backr face of thebrake band 31. A pivot;l of the link 58 in response toan outward thrust of the piston stem 60I-willmove the connecting link 61 away fromtthe brake drum 28'tof raise the brake band 31' from the face of thebrake drum-28: A`- retraction of the piston stern 60, or aventing of the cylinder 55 topermit such retractionwithout restraint, allowsfrom. the band 31 when the brake 110 is set for braking action with thebandV 31 tightly against the drumr 28; Uponray release of the brake the roller 63'will-support a lower portionv of the band 31 that has been moved radiallylfrom the drum. 28. Tosupport the roller 63 a bracket 64' is bolted to a support 65 rising upwardly from the'deck plate=112; l

Referring nowV to-Fig. 3, there is shown-the hoist cable spool assembly 16 as viewed from the right side of the shovel 1. From this side of the assembly 16 there is shown the'hoist cable spoolbrake 1111, which is substantially the same as the brake 110, and which operates in like manner; A spoolV shaft 66Y isin driving relation to' a hoist cable spool 67 uponI which is-wound the hoist cable) 17. Attached; to thecable spool 67 isan axially extending brakey drum 68.- A flexible brake band 69, ormed'in-two pieces and joined'at 70, surrounds a major .circumferential portion ofthe brake drum 68L and attacriedtotheradially inner faceof the band69 is a plurality of brake lining sections 711 Similarly, as in Fig. 2, one end of. the brake'band 69Y is' circumferentially xed by attachment to a link- 72 pivotally connected toa stationaryibracket 73 welded to a principal supporting frame 74: The oppositeendl of the-.brake-band 69-'is fastened toa circumferentially movable'A link 75 pinned toy a bell`A crank 762 Thebell crank 76; in'turn, is pivotally borne by an ear 77 fixed tothe supportingjframem. A long leverv arm 78 forming apartV set of lock nuts 85. y Thesupporting frame 74 is mountedupona deck plate Sl"of"the'cab"2.v A second supportingframe- 88 on the opposite side of the drum 68 is bolted in place on a main frame member 89, a portion only of which is shown. Supported by and bridging between the frames 74, 88 is a curved channel member 90, that is similar to the channel member 49 shown in Fig. 2. The channel member 90 is disposed radially outwardly from a major portion of the brake band 69 above the brake drum 68 to mount a plurality of brake band release support assemblies 53, that are identical to the support assemblies 53 shown in Figs. 2 and 4. The brake band release support assemblies 53, shown in Fig. 3, are each connected to the back face of the brake' band 69 for a purpose of operation identical to that of the assemblies 53 in Fig. 2 that are connected to the brake band 31.

A roller 91 is shown in Fig. 3, which is similar to the roller 63 in Fig. 2. The roller 91 is supported by a bracket 92 that in turn is bolted to a support member 93 rising upwardly from the deck plate 87. As shown in Fig. 3, the roller 91 is supporting the bottom portion of the brake band 69, the brake band 69 being in brake released position. With the brake released, the brake lining segments 71 are uniformly spaced from the brake drum 68 to eliminate any frictional engagement with the drum 68 that might occur in the absence of the assemblies 53 and the roller 91.

Referring now to Fig. 5, there is shown schematically the pneumatic control system for the dragline cable spool brake 110 of Fig. 2. The three release support cylinders 55 of the brake band release support assemblies 53 are each connected through the respective air inlet hose 59 to an air duct 94. The duct 94 is connected to one outlet port 95 of a tour way control valve 96. Thevalve 96 has a second outlet port 97 that joins with one end of a duct 98 that connects at its opposite end with the input side of a throttle valve 99.` A duct 100 that branches from the duct 98 connects with the outlet side of a check valve 101. The inlet side of the 4check valve 101 is connected to a duct 102 that joins with a duct 103. Duct 103 connects at one end with the outlet of the throttlevalve 99 and at the opposite end with the flexible hose 42 that feeds the brake releasing and setting cylinder 41. Each cylinder 55 houses a spring 108 that biases the associated piston stem 60 to a retracted position, and the cylinder 41 houses a bias spring 109 to urge the piston shaft 40 and the bell crank 37 to brake released position. l

The four way control valve 96 is provided with aninlet port 104 connected to a pneumatic pressure supply duct 105, and also with an exhaust port 106 which leads to the atmosphere. Forv operation of the valve 96 an electromagnetic solenoid 107 is provided which may be controlled from the operators station in the cab 2. A pneumatic control system similar to that of Fig. 5 is also provided for the hoist cable spool brake 111.

Digging operations with the dragline excavator 1 are accomplished in well known fashion through the manipulation of the hoist and dragline cables 17 and 22. The digging will be commenced by swinging the bucket 20 outwardly to the position shown in Fig. 1. To swing the bucket 20 to this position the dragline cable 22 will be drawn in on the spool 27, and the desired length of hoist cable 17 will be paid out to suspend the bucket 20 in pendulum-like fashion. The hoist cable spool 67 will now be held against rotation and the dragline cable 22 is then permitted to be paid out by allowing the spool 27 to run freely. The bucket 20 will swing toward the position shown and be brought to rest for commencing a digging stroke. The digging stroke is now made by drawing in the dragline cable 22 and paying out the hoist cable 17, as necessary, as the bucket 20 descends into the cut. Upon completing the digging stroke the dragline cable 22 may be reaved in an additional amount to raise the bail 25 and elevate the digging or open end of the bucket` 20. Through artful control of the hoist and dragline cables 17, 22 the bucket 20 may be raised to an elevation, while being retained at an angle of tilt to keep the load i to pivot without restraint.

within thebuc'ket, to provide clearance` for swinging ther cab Z'to a position where the bucket Z0may be upended to dump the load.

g In the manipulation of the bucket 20 the brakes 110, 111 are frequently brought into play, and both quickness of response and positiveness in moving betweenset-and` released positions are characteristics required for optimum operation.4 vThe loads handled require brake bands of considerable size, such thatwhen moved to released posi` tion in a manner to relinquish support for the bands upon y operating lthe brakes to set position. These characteristics of operation are of particular usefulness in manipulatingva dragline bucket.

To set either brake 110, or 111, the associated operating solenoid is deenergized. In the instance Vof the dragline cable spool brake110 deenergization of the solenoid 107 connects the outletfport 97 ofthe control valve 96 with the inlet port 104 to introduce air under pressure from the duct to the duct 98. The control valve 96 simultaneously connects the outlet port 95 with the exhaust port 106. The duct 94 and each of the release support cylinders 55 are then exhausted to the atmosphere. and hence through the throttle valve 99 and the duct 103 to `within the brake setting and releasing cylinder 41. The check valve101 will blockthe ilow of air and the throttle valve 99 is adjusted to Ycause a build up of pressure to occur within the cylinder 41 without objectionable inrush pressures, that might cause either an undue shock in the apparatus to be braked or an unwanted reciprocation of the piston shaft 40 due to rebound.

Piston shaft 40 is moved outwardly lfrom fthe cylinder 41 to pivot the bell crank 37 to move the link 36 circumferentially toward the link 34. The brakeband 3,1and the brake lining segments 32, are wrapped tightly about the brake drum 2.8 to retard rotation of the spool`27.

AsV pressure builds up `within the cylinder 41 the interiors of the release support cylinders 55 of the brake are brought to atmospheric pressure by venting of` the duct 94 through the control valve 96. With atmospheric pressure prevailing in the cylinders 55 the springs 108 retract the piston stems 60 and the links 58 are free Thus, there will not be opposition to movement of the brake band 31 radially inwardly to brake setting position. A v

To release the brake band 31 from braking engagement' with the drum 28 the solenoid 107 is energized to shift the four way control valve 96. The valve 96 will now connect the outlet port 97 to the exhaust port 106 to vent the brake setting and releasing cylinder 41. The check valve 101 freely permits ilow of air from 4the cylinder 41 to the atmosphere, and the spring 109 is of size to rapidly retract the piston shaft 40 and shift the link 36 circum -r ferentially to effect an increase in diameter of the `band 31.

The valve 96 also connects the release `support'cyl-vinders 55 to the inlet port 104 to introduce pressure with-l vicinities of the assemblies 53 will be spaced and sup- A ported from the drum 28 by the action of the cylinders 55.

Since the` brake band 31 and brake lining segments-v Air under pressure will `pass through the duct 98 facer-ofi the:,band.= 31 will then bear upon'the roller 63,-

for: the.: supporti that?. is necessary, andi thebrake lining segments." 32; will: be: uniformly spaced. from the. drum 28v fon the: full: extentf, of: the banditi.y Thev spool. 27 may` rotate in: response. to.- Vdrivemechanism attached to the shaft 26:'without'.interference: of thei brake 1:10.'

InsFigfi 3;ithe briakefl'llgis'ishown in brake released positiontand. assumes:v at spaced relation1 for the brake liningesegments=7^1 asi has beendescribed with reference to the: brake; 110.( operation' of thegbrake 1111 is like that described in-i connection: with the brakey mechanism O Pigs 2f.v

s Thereisathuss provided zusetof` brake 110, 111 adapted to be employed directly upon thecable spools of an excavator thatexhibit the necessary characteristic of quick positive'respon'sey in being shiftedrbetween setand released positions; inbrakes having;ban= sizes-for handling large loads, and in'whichihere is no danger of thel bandsgcollapsingagainst thebralke drums when in released position.

Y If claim:

1.. In a frictiony brakeV the combination? comprisingV ay brake: drum; at brake band, in 'Yfacinggrelation to said' drum with: any end- 'relatively shiftable: circumferentially withres'pect. to said'f drurn`- to wrap the band tightly'aboutthe drum'fory effectinga brakingaction and-to release the band topermit the samel to'be spaced'from the drum; a brake actuator engaged. with: said brake band to wrap the band' about the drumfor etectingsaid braking: action andy to release the: band; and a fluid pressure operated band supporting; operator having positions of rest4 and opera-- tion cooperatively.I engaged with' saidv brake band to -move' a-portion of. saidband. away from said'drum when operated'for. spacing the band and drurn` from one another when said' band` is released, and when'in positionv oftrest permittingsaidbandtofbe moved into tightly wrapped positionwith: respect -t'oV said drum.

V21. In: a friction brake the combination comprising a brakedrum;V a brake band intfacingl relation to said drum with an end. relatively:Y shiftable circumferentially with respectsto `said drumtowrapthe bandvtightlyiabou-t the' drum. for effectingv al braking; action and to-releasez the band to. permit theesarne to be spaced from the drum; a uid p ressureA operatedband supporting operator having, positions of res-t andoperationV cooperatively engaged with said brake band to move a portion of said bandaway from=said drum when operatedifor spacing the band and; druml from f one: another when said bandy is released,

andwhenin position of' restpermitting said band to be moved-into tightly wrapped-positionv with respect to said drum; abrake actuatorattachedfto. an end of said brake bandv to shift said band end circumferentially in onezdirectionforI brakingtactionandin. the other direction for release-o'f'-saidband; andoperating means for said band supporting operator andsaid brake. actuator for alternatively operating said operator and actuator whereby said actuator retains said: bandend'l shifted for braking action whenfsaidfoperator is at rest andsaid operatorvis in positionv of'. operation when said actuator retains said band end infbrake releasing position.

v3.- Inafrictionlbrake the combinationl comprising a brake drum; abraketbandin acingyrelation to said drum with an end relatively; shiftable circumferentially with positions: of rest: and operation cooperativelyy engaged withsaid'brakeband to'move a portion of .said band away from said drum when operated for spacing the bande` and l drum: from. one.- another: when: said band :iszre- Thischaracteristic isv4 incorporated 8 leased, andwhe'n in positionotrest:permittinggsaidrband. tof be moved? into tightlywrappedy position. with. respect. tot saiddrurm, andfa iuidwpressureio'perated,- brake actuator' having pesitions'- of' rest#- and .actuationA attached tol an end.-

connections between the rst valve outlet andn saidf band(` supporting operatorg secondY uidduct connections. between',l the second valve: outlet; ande. said brake actuator;l and controlling means forsaidavalve alternatively' placing. said* valve: in 'a position-'joining` th'e rst' outlet tol the; exhaustaird-:the Ysecond valve.outlet-A tothe inletandfanother position .joiningthe` second valve outlet to theexhaust and `the irst; valve'foutlet to'` the inlet.

5. Inl av` friction# brakes the y,combination comprising aA brakefdrurn;.a'zbrakebanddh acing'relation, to said drum adaptedto bernovedsinto a braking positionagainst said' drumfand intofa' released positionwherebythe band may bes-spaced from said d'rum,actuating means engaged with an: end` ofiv saicLbandf for moving:said` band between saidbraking and released positions, a link pivoted between its-vends', a-:connection `between one end of said link and said;brake'bandjoiningthe link to the bandl at a point intermediate` therends; of: thesbandg, and a iluid pressurew connection between one; end of: saidlink and? said brake band; and a'forcevexerting operator adapted to be alternatively placed: in actuation .and at, rest cooperativelyv engaged withithe opposite: end'ofsaid link :adapted to vapply a working force when actuated to cause said link to pivot" andmoveifa*` portion off saidz brake band through said'l connection away: from said brakeV drum and to diminish'said workinggforcewhen placed at rest.

7. In arfriction brake the combinationcomprising a brake drum,` aib'rakeV band in facingrelation. to said drum adapted toxbe moved:intoiazbraki'ng-l position against said, drum and into afrelease'd positionV whereby the band may be spaced fromlsaiddrumgtactuating means attached to;

anl end of/saidband formoving saidy band into braking position,v and a'- force exerting.'y operator adapted to-be alternatively placed in'. actuation'fand atrest cooperatively engaged withsaid` band. at aspoint intermediate the band ends adapted-.toapply a5 working force. whenA actuated to! said' band to movefaiportion of the band away from saidbrakedrurn and totvrelievesaid'band of said. working,- forcewhenlatlrest.-

8. 'In a frictionk brake' the combination` comprising a! braked'rurn; a-brakei-b'a'ndin facing. relation toisaid drumI adapted to bemoved` into a braking-position against saidH drum'and: into areleased position whereby therband may be spaced from"said drum; actuating'means `for movingV saidband Vbetween said braking andtreleased positions; a linkl pivoted betweenits ends; a connection between` onefenclofy said link' and saidbrake. band; a'fluid pressure: operatorr adaptedito be alternatively placed in. actuation zand at .rest cooperativehv engaged: with the opposite end ofzsaidlinkto apply a force` upon actuation tosaid link lto 'pivot the, samerand'. move aportion, of said brakel band through Vsaid `connection awa-y, from :saidsbrake drum,

and to arelieve; .said .1 linkt ofl said -force when atgrest; and

control means for said actuating means and said operator to retain said operator in actuation when said actuating means has moved said band to released position and to retain said operator at rest when said actuating means has moved said band to braking position.

9. In a friction brake the combination comprising a brake drum; a brake band in facing relation to said drum; a rst uid pressure cylinder having a brake actuating piston cooperatively engaged with said band to alternatively place said band in brake set and released positions; a plurality of brake band supports each including a uid pressure cylinder having a piston movable between positions of actuation and rest and cooperatively engaging said band to hold the same from said drum when in actuated position and to permit said band to be placed in brake set position when in the position of rest; control valve means having a vent, an inlet, and a pair of outlets that may be alternatively connected to said vent and inlet, whereby upon connection of one outlet to said inlet the other outlet is connected to said vent; and fluid connections joining said rst fluid pressure cylinder to one of said outlets and joining said brake band support cylinders to the other of said outlets, the control valve means in one position applying fluid pressure to said rst cylinder for setting the brake and venting said support cylinders, and in another position applying uid pressure to said support cylinders to place the piston thereof in actuated position and venting said cylinder.

10. In a friction brake the combination comprising a brake drum, a band circumferentially extending about a portion of said drum adapted to be brought against said drum to effect braking action and to be moved from said drum for brake release, a brake actuator for said band to move the band against said drum for said brak- 10 ing action, a force exerting release support cooperatively engaged with said band having an actuated condition wherein a force is exerted upon said band capable to support a section of the same from said drum and a relaxed condition wherein said force is diminished, and control means for said brake placing said release support in actuated condition when said band is to be retained in position removed from said drum and placing said release support in relaxed condition when said band is brought against said drum by said brake actuator.

l1. In a friction brake the combination comprising a brake drum, a band extending about a portion of said drum adapted to be brought against said drum to effect braking action and to be moved from said drum for brake release, a plurality of force exerting release supports spaced along said band and cooperatively engaged with said band at points intermediate the ends thereof each having an actuated condition wherein a force is exerted upon said Iband capable to support a section of the same from said drum and a relaxed condition wherein said force is diminished, and control means for said brake placing said release supports in actuated condition when said band is to be retained in position removed from said drum and placing said release supports in relaxed condition when said band is brought against said drum.

References Cited in the le of this patent UNITED STATES PATENTS 

